Recently, there have been an increasing number of instances in which a centrifugal blood pump is used as a heart assisting pump for assisting a heart or for extracorporeal blood circulation in a pump-oxygenator. Proposals have been made of a centrifugal blood pump of the type embedded in a living body.
One example of a centrifugal pump involves a system in which a driving torque from an external motor is transmitted by use of magnetic coupling, in view of the fact that physical communication between the exterior and a blood chamber in the pump is totally precluded so that penetration of bacteria and the like can be prevented. Such a centrifugal blood pump includes a housing having a blood inlet port and a blood outlet port, and an impeller which rotates within the housing and which feeds blood by a centrifugal force during rotation. In addition, the impeller is provided with a permanent magnet, and is rotated by a rotation torque generating mechanism which includes a rotor having a magnet for attracting the magnet of the impeller and a motor for rotating the rotor. The impeller is attracted also toward the opposite side to the rotor, and is rotated without contacting with the housing.
In the centrifugal blood pump apparatus of the intracorporeally embedded type described Japanese Patent Laid-open No. 2003-135592, a metallic material is used for making the housing for the purpose of using the apparatus for a long time. On the other hand, the blood pump apparatus described in Japanese Patent Laid-open No. Hei 09-122228 and the blood pump apparatus described in Japanese Patent Laid-open No. Hei 11-244377 use a plastic material to form the housing. The housing in this case is required to have a certain extent of thickness for securing strength of the main body of the pump apparatus, and this structure leads to a concern that the rotating magnetic force applied to the impeller by the impeller rotational torque generation section might be lowered.